milan



Reissued Apr, 26, 1932 UNITED s'n l'res PATENT "OFFICE ueo rnsra nozza,or MILAN, ITALY, nssrenofi r0 socmra rrnmana rrnmr, or

' mnaiv, ITALY MANUFACTURE or RUBBER ARTICLES No Drawing. Original No.1,717,248, dated .hinell,

1929,,Seria1 No. 204,421, filed July 8, 1927, and in Italy January 31,192 7. Applicaticn for reissue filed June 11, 1931. Serial No. 548,729.

The present invention relates to certain new. and. useful'improvementsin the treatment of coagulable aqueous dispersions of rubber, such forexample, as rubber latex in itsnatural or concentrated condition, withtheobject of causing their-thickening and coagulation under givenphysical conditions .50 as to enable the rapid and sure manufacture of agreat variety of rubber articles. It is a well known fact that naturalor preserved rubber latex, both diluted and concentrated, behaves indifferent manners when treated with different chemical substances,organic or inorganic: some of which do not alter appreciably thephysical features of the latex; others on the contrary, eitherimmediately or after a certain time, give rise to the coagulation of theparticles of rubber in suspension in the latex. Naturally among thelatter chemical substances are chosen those which are used or have beenproposed for coagulating the rubher from thelatex. In order to obtainsaid coagulation, it is however necessary that the concentration of thecoagulating substance in relation to the latex be maintained above acertain minimum value. Iflower concentrations are usedit is possible, byadding to the latex substances apt to preserve it, to prevent the latex,when left to itself, from being subjected to alterations: the latex cansimply thicken withsaid salts, diluted or in suspension in water,

or else of converting the latex into a mass flowing less readily andconseq llently better suited for the purpose in View. It is a known factthat such compounds, whether dis solved or simply held in suspension inwater, when added to the latex can produce coagulation, or, when addedin less quantity, can

thicken the same in proportion to the concentration of the compound withregard to the latex;

. But such salts, like many other materials,

have another action upon latex which was altogether ignored heretoforeand which forms the chief featureofthe presentinvem tion.

If said salts are added to latex in very l small proportions, forinstance in the ratio .of about 3 grams of calcium sulphate dissolved orheld in suspension in water for 1000 grams of dry residuum'ot latex andthe treat the latex, the thickening increases with the temperature andwith the time this temperature is applied, up to complete coagulation.Naturally the higher the temperature, the

greater will be the thickening and the quicker will be the coagulation.Coagulation is very rapid at temperatures above 75-80 C. and almostinstantaneous at such temperatures when the latex is slightly shaken.

The coagulum obtained when the mass is not shaken, canhave a very slightconsistency, appearing as a suspension of very minut particles in theaqueous phase or can be compact and resisting notwithstanding itsenclosing all the serum. 7

The one or theotherlcase may occur according to the compound orcompounds added (it is obvious that mixtures of saltsof bior trivalentmetals can be used) or the same or of any one of them can be added tothe rubber."

latex together or separately, with gasoline or other chemical bodieswhose, presence-canhave the object of promoting or controlling,

the thickening process or the coagulation. The addition 'ot such bodiescan be easily obtained when the same ardissolved or held in suspensionin water or any other sol 'vent, chosen according to the special properstance ammonia. The latex ought also to contain a preserving-agent; itcan have its original rubber content or be concentrated; it-can containin solution or in suspension vulcanizing agents, colouring matter orfillers, as, for a'm'ilyiilg the process here described, it issuilicient that it be stable in the conditions under which the abovestated substances are added, and that between these substances and anyothers that mayhave been previously added to the latex,

.no chemical reaction should take place that may cause an untimelycoagulation.

Confining the example to the description of the behaviour of salts ofbior trivalent metals, it may here be stated that quantities not greaterthan 1.5 grams of a soluble or slightly soluble salt of calcium and 1gram of zinc-oxide, in suspension in a few cubic centimeters of ammoniaadded, stirring all the time, to 1000 grams of latex preserved withammonia and containing 50% of rubber, or else quantities not-greaterthan 1.5 grams'of calcium salt by suspension in a few cubic centimetersof ammonia. water added while stirring, to 1100 grams of latex having50% of rubber preserved with ammonia, and containing 100 grams ofbenzole or of gasoline, cause a light thickening, when the adties.

dition of said chemicals and the preserving of the latex are carried outat a temperature lower than 20 C., but are suificient to cause a veryrapid thickening and coagulation when the latex is brought for asuflicicnt time to a higher temperature, under 100 C., a few minutesbein V tain coagulation at about -97 C.

There are many organic or inorganic bodies which have a similarbehaviour.

While I have here described the behaviour of a given class of bodies,such description is by no means to be understood as indicating that thesame procedure cannot be extended to other bodies, of however vdifferentchemical constitution, the object of said description being purely toexamine the action of the bodies mentioned on latex with regard to theirthickening and coagulating proper Having thus described the preliminarytreatment which the dispersion has to undergo, a few illustrations willnow be given, des'crlbing some processes of manufacturing rubberarticles, and some possible applications due to the special features andproperties acquired by aqueous rubberdispersions when treated accordingto this invention.

Some of the articles (folinstance tea-ts, bulbs for dropper tubes,surgical gloves etc.)

haveheretofore been manufactured by using pure, rubber solutions orrubber-scrap solutlons gasoline. Suitable moulds are suflicient, forinstance, to ob layer of rubber. The operation is repeated several timesuntil the desired thickness is obtained, the articles being thenfinished, vul- ('anized and stripped from the mould.

It is evident that the expense from gasoline loss, which is large evenif special apparatus for recovering the solvent be used, combined withthe time required by this process make it a rather costly proposition.

It has been proposed to use, instead of gasoline or .benzole solutions,diluted or concentrated rubber latex, following the same process, butnotwithstanding its advantages such a method has the drawback ofrequiring a great length of time for drying the layers of rubber.

Moulds of porous material have also been suggested, which, by partiallyabsorbing the latex serum, allow 'a thicker layer of rubber to depositat each dip; but even this process,

besides being suitable only for manufacturing'thin rubber, articles, hasmany drawbacks which make it rather difficult to apply.

The process hereafter described solves the problem entirely and by usingit'the manu facture of rubber articles on forms or in moulds is renderedso quick and cheap, that it can be extended to many other articles made'at present in other ways.

A suitable form or mould or core or a certain number of the same is hungfrom a.

convenient support in such a way as to be uniformly heated for instanceif the moulds are hollow, by circulating hot water through them. Saidmoulds are dipped in a trough containing natural or concentrated latex,v:

With or without vulcanizing agents,'col0urin}; matter .or fillers,prepared as described above and preserved at such a low temperature asto prevent coagulation. After heating the moulds as above stated at aproper temperature and keeping them in the ba h for a convenient lengthof time. they are taken out coveredwith a layer of thickened latexadhering to them, which layer rapidly coagulates and, after having beendried, becomes a rubber layer whose thiclmess depends on the temperatureof the mould and on the length of time of the dip.

If for instance water at 95 C. is used to heat the mouldor core,layersof dry rubber be stripped or not from the moulds and sub.-

vsequent-1y vulcanized according to the latex composition. e,

The surface of the articles thus manufactured is smooth and thethickness more uniform than those obtained from gasoline solutions ofrubber.

This process of local coagulation through. local heating of the wallupon which the layer of rubber is to be deposited, is entirely new andconstitutes the outstanding prine ciple of the resent invention.

The manu acture of inner tubes for tires,

tubing, etc. can,be carried outin this way;

and in such case a. core is used Whose outer diameter is equal to theinside diameter of the tube to be obtained and which can any: how beconveniently heated. It can be dipped in the latex, 'heatedand taken outafter the layer of coagulum has formed on it, or else, after having beenbrought to a proper temperature, it can be shifted along in the bath oflatex with a continuous motion. The tube so formed can then be treatedas above described.

If the article to be manufactured cannot be 4 formed on a core ormandrel, the process can be modified as follows: The mould whose insidesurface has the form and dimensions of the article to be obtained, ismade of several built-up pieces so asto form a cavity with an opening,which cavity is filled with latex having undergone the treatmentdescribed above, and the mould. is then uni formly heated from theoutside to the re-' quired temperature and for the time required toobtain the thickness of rubber wanted. The fluid latex is then pouredout and air, which may be heated, is blown into the cavity of the mould,which latter after a certain time can be allowed to collapse leaving thearticle ready for further treatment.

. By the same process it is possible to manufacture rubber sheets bybringing in contact, by any appropriate means, a heated sur face withthe latex prepared as above described, and if the surface be a cylinderpartially dipped in the-latex for its whole length and revolvingcontinuously,the layer of coagulated rubber can be detached as soon asit comes out of the latex, thus obtaining a.

continuous strip of rubber whose thickness depends on the temperature ofthe surface of the cylinder and on its speed.

If a fabric or-a set of threads, yarns, cords or ribbons, be made tomove along the heated metallic surface in the latex, at'a proper speed,a'very simple and convenient method of waterproofing or rubberizingfabrics canbe developed.-

' properties gained by latex. after the above described treatment, isthe. manufacture of articles such as threads, cords, small tubes,

Another interesting application of the.

etc., heretofore costly methods;

It has already been pro osed to manufacture these articles from ru berlatex, natural or concentrated, by letting it flow into a medium havinga high coagulating action. The very rapid coagulation of the Stream oflatex flowing out of a nozzle should allow it to retain the form anddimensions which the latter has at the exit.

Evidently this could only be obtained with prepared by other long andarticles of a small section and size, as coagulation can take place withthe necessary speed only on the superficial'layers of the thread so thatthis method; has not found any practical application.

The process here proposed obtains this object in a much better and morepractical Way.

A trough of latex prepared as above is connected to small pipes ornozzles whose inside'section has the form and size of the articlewanted.

The pipe can be heat-ed by suitable means to a convenient temperaturetowards the nozzle end: the latex is forced into the pipes t byexerting, for instance, a pressure on the Hereabove have been described,.as exam ples, a few ways of manufacturing various articles whichillustrate some applications of the properties of latex after thetreatment described: obviously any other process which, by means of anymechanical device or physical apparatus, can be used to manufacturerubber articles or to rubberize fabrics, or which can be used for anyparticular object. in the treatment of rubberdispe'rsions as .describedabove,a'ccording to which the dispersions, pre-rendered heat-unstablewards coagulation, are subjected to local heating to; the coagulationtemperature through the same surface uponwhich the coagula'ted rubber isto be deposited, is to be considered within the limits of the presentinvention.

It willbe appreciated from the' foregoi ng description that theinvention may be appligll to the direct manufacture ofrubber objec s ina great variety of ways, by, for instance, internal .or a external,

moulding, whether such moulding be conducted statically, as by thesimple procedure of dipping a heated shape into the prepared dispersionand by introducing, the prepared dispersion into the interior of ashape, or by causing a heated surface to travel through the dispersion,or conversely by causing the prepared dispersion to flow over a heatedsurface; and the term forming element used in the claims is to beunderstood as comprising the various devices which may be employed forlocally heating the prepared dispersion for the production of varioustypes of rubber ar' ticles. The expression forming element thereforecomprises internal and external moulds as ordinarily understood, as Wellas devices which confer but a temporary shape upon the article, suchasthe rotating cylin-' der above. described, and nozzles and like means intheir diverse forms employed for ill extrusion. I

What I claim as my-invention is: 1. A process of manufacturing rubberarticles I which comprises subjecting a coagulable aqueous rubberdispersion containing such an amount of coagulating agent as willcoagulate the dispersion solely at raised temperature to local heatingto the coagulation temperature of the dispersion at the surface whereatthe rubber is to be formed so as to produce upon that surface a layer ofcompact coagulated rubber. F

2. A process of manufacturing rubber articles which comprises subjectinga coagulable aqueous rubber dispersion containing. zinc oxide and suchan amount of coagulating agent as will coagulate the dispersion solelyat raised temperature to local heating to the coagulation temperature ofthe dispersion at the surface whereat the rubber is to be formed so asto produce upon that surface a layer of compact coagulated-rub- 3. Aprocess of manufacturing rubber articles which comprises subjecting acoagulable aqueous rubber dispersion containing vulcanizing ingredientsand such an amount of coagulatingagent as will coagu:

late the dispersion solely at raised temperature to local heating to thecoagulation temperature f the dlspersion at the surface whereat therubber is to be formed so as to produce upon that surface a layer ofcompact coa'gulated rubber.

4. A process of manufacturing rubber articles which comprises subjectinga coagulable aqueous rubber dispersion containing such an amount of aninorganic coagulating agent as will coagulate the'disperslon V solely atraised'temperature to local heating to the coagulation temperature .ofthe dispersion at the surface whereat the rubber is to be formed so asto produce upon that sur face a layer of compact coagulated rubber.

5. A process of manufacturing rubber articles which com rises subjectinga coagulableza queous ru ber dispersion containmg such arkamount ofcoagulating agent as the forming element in contact with the willcoagulate the dispersion solely at a temperature substantially between100 C. to local heating to a temperature. within'saidrange at thesurface whereat the rubber is to be formed so as to produce upon thatsurface a layer of compact coagulated rubber.

6. A process of manufacturing ru beiarticles which comprises subjectinga coagulable aqueous rubber dispersion contain ing zinc oxide and suchan amount of coagulating agent aswill coagulate the dispersion solely ata temperature "substantially between 70-100 C. to local heating to'atempcrature within said range at the surface whereat the rubber is to beformed so as to produce upon that, surface a layer of com pactcoagulated rubber.

7. A process of manufacturing. rubber' articles which comprisessubjecting a 'coagulable aqueous rubber dispersion containing such anamount of an inorganic coagulating agent as will coagulate thedispersion olely at a temperature substantially between i0-'-100 C, tolocal heating to a tempera ture within said ran 'e at the surfacewhereat formed so as to produce the rubber is-to be upon that surface alayer of compact coagulated rubber.- i

8. A process of manufacturing rubber articles which comprises subjectinga coagulable aqueous ru ber. dispersion containing such an amount of awater soluble salt of a divalent metal as will coagulate the dispersionsolely at a temperature substantially between 70100 G. to local heatingto a temperature within said range at the surface whereat the rubber isto be formed so as to produce upon that surface a layer of compactcoagulated rubber.

9. A process of manufacture of rubber articles which comprises brin inginto contact a coagulable aqueous rub rdispersion containing such anamount of coagulating agent as will coagulate the dispersion solely at atem erature substantially between 7 0 -l00- and a heatedv formingelement heated to a temperature within said range so as to produce uponthe surface of the forming element in contact with the dispersion alayer of compact coagulated rubber.

10. A rocess of manufacturing rubber articles w ich comprises bringinginto contact a coagulable aqueous-rubber dispersion containing zincoxide and suchan amount of coagulating agent as will coagulate the disrson solely at a temperature substantially jtween70-100 C. and a heatedforming element heated to a temperature within saidrange so as toproduce uponthe surfacelof (1S- persion a layer of compact coagulatedrubber. v

11. A- process of. manufacturing rubber articles in lengths whichcomprises extrudinga coagulab e aqueous dispersion of rubber containingsuch an amount of coagulating agent as will coagulate the dispersionsolely at raised temperature through an extrusion device heated to thecoagulation temperature of the dispersion.

12. A process of manufacturing rubber articles from latex, comprisingthe steps of adding to the latex such an amount of coagulatingagent aswill coagulate the latex'solely at a temperature between 70100 (l;bringing the latex into contact with a forming element; heating thelatex through the forming element to said temperature to effectcoagulation; and drying the coagulated latex.

13. A process ofmanufacturing rubber articles from latex, comprising thesteps of adding to the latex such an amount of coagulating agent as willcoagulate the latex solely at a temperature between 7 O100 0.; bring ingthe latex into contact with a forming element; and heating the latexthrough the forming element to said temperature to effect coagulation.

14. A process of manufacturing rubber articles from latex, comprisingthe steps of adding to latex which has previously been subjected to apreserving treatment with ammonia such an amount of coagulating agent aswill coagulate the latex solely at a temperature between 7 0-100 0.;bringing the latex into contact with a formin element; and heating thelatex through the forming elementto said temperature to effectcoagulation.

adding to latex which has previously been subjected to a preservingtreatment with ammonia such an amount of a soluble metal salt as willcoagulate the latex solely at a temperature between 70100 0.; bringingthe latex into contact with a forming element; and heating the latexthrough the forming element to said temperature to effect coagulation.

17 A process of manufacturing rubber articles from latex, comprisingthe-steps of adding to the latex such an amount of coagulating agent aswill coagulate the latex solely at a temperature between -'100 (3.;

ticles from latex, comprising the steps of adding to the latex such anamount of coagulating agent as will coagulate the latex solely at atemperature between 709-100" C.;'

ticles from latex, comprising the steps of adding to the later; such anamount of coagulating agent as will coagulate thelatex solely at atemperature between 70100 (3.; bringing the latex into contact with aforming element; an d heating the latex carried by the forming elementthrough the latter to said temperature for a period sufl'iciently lon toobtain a coagulated layer of the desire thickness.

20. A process of manufacturing rubber articles from latex, comprisingthe steps of adding to the latex such an amount of a soluble metal saltas will coagulate the latex solely at a temperature between 70-100 (l;bringing the latex'into contact with a form ing element; and heating thelatex carried by the forming element to said temperature for a periodsufliciently long to obtain a coagulated layer'of the desired thickness.21. A process of manufacturing rubber articles from. latex, comprisingthe steps of adding to the latex such an amount of a soluble metal saltas will coagulate the latex solely at a temperature between 70100 0.;bringing the latex into contact with a forming element; and heating thelatex carried by the forming element through the latter to saidtemperature for a period sufliciently long to obtain acoagulated layerof the desired thickness. k

22. A process of manufacturing rubber articles in lengths from latexcomprising the steps of adding to the latex such an amount ofcoagulating agent as will coagulate the latex solely at a temperaturebetween 70- 100 C; and carrying the latex through an extrusion deviceheated to within said temperature range.

UGO PESTALOZZA.

brin ing the latex into contact with a. forni- A ing e ement; andheating the latex carried by the forming element to said temperature fora period sufliciently long to obtain a coagulated layer of the desiredthickness.

18. i A process of manufacturing rubber ar-

